The field of use of the present invention extends to ships' propulsion systems, preferably in the field of yacht construction. Here, usually internal combustion engine-driven ships' propulsion systems with preferably one or two propellers are used. They are caused to rotate via a transmission downstream of the engine. While the engine is usually controllable with respect to its speed, to determine the cruising speed of the ship, the transmission is usually switchable with respect to the sense of rotation to select between forward and reverse.
In many cases, the transmission is also integrated in a clutch adjustable with respect to its slip, where a trolling speed is controllable by varying the clutch's slip. At this trolling speed, the engine speed usually remains constant in the range of the idling speed, while the driving speed of the ship is determined by varying the slip of the clutch. Trolling operation created in this manner can be used, for example, when crawling in port or during high sea fishing.
EP 0 524 992 B1 discloses a generic control device. It comprises control and sensor means for influencing the engine speed, and the slip of the clutch, and is connected on the input side with a control-signal generator to select the driving direction and speed of the ship by operating at least one control lever, wherein the control lever is used to adjust a propeller shaft speed and sense of rotation, the adherence to which is closed-loop controlled by the control electronics in such a way that a mode of operation is freely defined as a function of the operating parameters of the engine and the transmission to be adhered to, which can be either a first mode of operation, in which the propeller shaft speed and sense of rotation is created with the clutch engaged by changing the engine speed, or a second mode of operation, wherein the propeller shaft speed and sense of rotation is created with a predefined engine speed by varying the slip of the clutch.
The sensor means required for closed-loop controlling of the clutch operation leads to substantial electronic overhead. Furthermore, the variation of the slip of the clutch is abrupt. This is because the adjustment value for the adjustable clutch is varied directly in response to the setpoint value. This leads to high mechanical stresses on the drive train, in particular during maneuvering.